German Laid-Open Patent Publication No. 36 03 134 describes a wall plug anchor assembly for light-duty concrete and like concrete compositions. This known wall plug anchor assembly includes a sleeve body made of a thin-walled piece of pipe or tubing and its head end has a conically or outwardly widened portion.
This prior-art wall plug anchor assembly is particularly suited to be driven into bricks, blocks, and plates. These components might be made of gas-expanded and light-duty concrete, foam-type concrete, or clay and/or silicate-type concrete.
Into the thin-wall prior-art wall plug anchor assembly are cut at least two diametrically arranged slots, extending from the tail or foot end thereof. A spreading body can be introduced, from the foot end of the sleeve, into the sleeve, and this spreading body serves to spread or flare the legs which remain between the slots, so as to anchor, embed, or fasten them in the surrounding light-duty concrete material.
The particular spreading body can be a sphere which is initially positioned at or in the tail end, i.e. the end opposite the head end of the wall plug anchor assembly. This sphere has a diameter which is greater than the inner diameter of the sleeve body.
The spreading or flaring in this prior art wall plug anchor assembly is achieved by forcing the sphere through the tail end, for flaring or spreading of the legs formed in the longitudinally slotted portion, and the legs are anchored accordingly.
However, this anchoring system does not apply in the case where a bore hole is first drilled into the particular construction component or structure, as is done in the case of heavy-duty type concrete and like compositions.
In a further embodiment of the prior-art wall plug anchor assembly of German patent publication No. 36 03 134, the sphere which serves as the spreading body, or a conical wedge, is formed with interior or female screw-threads which cooperate with exterior screw-threads of a bolt. The bolt, in turn, has a head end which can abut against the head of the sleeve.
Upon tightening of the bolt, the spreading body, sphere, or conical body, can be forced into the slotted section of the sleeve for flaring and anchoring of the legs which remain between the slots.
One might assume that the anchoring system or assembly according to German patent publication No. 36 03 134 can be equally utilized in applications in which a bore hole is preformed in the concrete material, since the legs might be flared or spread for anchoring, upon tightening or turning of the respective bolt to move the particular spreading body that is being used.
However, it has been found that such a prior-art wall plug anchor assembly can only be successfully used with gas-expanded or light-duty concrete and the like material, so that the flaring or spreading of the legs can be attained to yield satisfactory retention and safety values or margins.
Furthermore, in the prior-art wall plug anchor assembly it is a requirement that the bolt cooperating with the spreading body, i.e. the sphere or the spreading cone in its place, also be the actual securing element by means of which other construction members can be secured by the wall plug anchor assembly to the concrete body or structure, for example a wall. If a securing element other than the bolt is used in the wall plug anchor assembly, it would remove the spreading body from its frictional engagement in the sleeve, namely the flared section thereof, and its flaring might be reversed upon application of pulling (tensile) forces, thereby eliminating the anchoring action of the sleeve.